A Reliability-Aware Edge–Cloud Framework for Early Intrusion Detection in IoT Networks

Gateway-resident intrusion detection can act before IoT traffic reaches cloud services, but early decisions are based on incomplete flow prefixes. This paper presents a reliability-aware edge–cloud framework that treats early detection as a sequential routing problem. At each checkpoint, a lightweight gated recurrent unit (GRU) maps causal packet-prefix features to a malicious-probability estimate. Temperature scaling, asymmetric benign and malicious thresholds, and an eight-packet minimum-evidence gate determine whether a flow exits locally, remains under observation, or is sent for cloud refinement. Short and unresolved flows are classified by regularized logistic regression using a compact 97-feature causal representation. The edge model contains 19,777 parameters, and each cloud submission carries 388 bytes of float32 features. The principal evaluation uses all 309 CIC-IoT-2023 PCAP files under four outer PCAP-disjoint folds, with separate edge-training, calibration, cloud-development, and final-test roles. Across 2,286,754 pooled out-of-fold flows with 88.54% malicious prevalence, the framework resolves 422,190 flows at the edge and routes 1,864,564 for cloud refinement, reducing cloud submissions by 18.46%. The final policy attains 4.47% FPR, 1.89% FNR, 96.82% balanced accuracy, and 98.76% F1 score. Observation-budget analysis identifies 32 packets as a corpus-specific compromise, whereas controlled delays in post-eight-packet information expose the limits of short-prefix detection. On the balanced CICIDS2017 test set, in-domain development attains 97.03% balanced accuracy; zero-shot transfer falls to 86.30%, and target-calibration-only adaptation improves it to 91.65%. Ablation results identify the minimum-evidence gate and cloud-refinement stage as the main reliability controls. Benign false alarms, delayed post-eight-packet information, cross-dataset shift, and scenario/file-level labels remain the principal limitations.